Index of content:
Volume 91, Issue 10, 15 May 2002
- HEAD/MEDIA INTERFACE AND TRIBOLOGY II
91(2002); http://dx.doi.org/10.1063/1.1452697View Description Hide Description
Pole tip recession (PTR), which is caused by differences in wear resistance of the various phases in magnetic disk and tape heads, must be reduced because it is probably the main impediment to reduction of spacing. Here, a numerical model of PTR is presented. Experimental results suggest that three-body abrasion, which leads to primarily plastic wear, is the mode responsible for PTR. In the model, the authors assume this wear mode, and assume that wear is a function of load, sliding distance, hardness of the worn surface, and dimensionless wear coefficients. As sliding proceeds, PTR increases continuously, which leads to a continuous change in contact between three-body abrasives and poles; the load carried by the poles decreases as PTR increases. This is modeled by assuming that asperities of the head and medium deform and wear plastically to accommodate passage of particles through the interface. The pole wears less as PTR increases since the opening for sliding particles increases. This accounts for the decreasing rate of change of PTR with sliding distance found for disk and tape heads numerically and experimentally. For tape heads, the model predicts that each of the following leads to higher PTR: increasing the thickness of three-body particles, increasing tape tension, decreasing pole hardness, and increasing the pole wear coefficient.
91(2002); http://dx.doi.org/10.1063/1.1452698View Description Hide Description
This work reports a novel method for the visualization of slider-disk or slider-particle-disk interactions. The method is based on a special testing disk which is same as the conventional magnetic disk media except using a layer of magneto-optical (MO) material to replace the magnetic layer of the magnetic disk media. The magnetization in the MO layer will be switched by a small external field applied if the temperature generated by the interactions is higher than the Curie temperature of the MO material. The proposed method and corresponding setup were used successfully in the experimental study of slider-disk and slider-particle-disk interactions.
91(2002); http://dx.doi.org/10.1063/1.1452699View Description Hide Description
A technique to perform nanofatigue experiments was developed. This technique utilizes a depth-sensing nanoindenter with harmonic force. The nanofatigue behavior of 20 nm thick amorphous carbon coatings was studied. The contact stiffness was monitored continuously throughout the test. The abrupt decrease in the contact stiffness indicates fatigue damage has occurred. The critical load amplitude, below which no fatigue damage occurs, was identified. It was found that the filtered cathodic arc coating exhibits longer fatigue life than a direct ion beam coating. Failure mechanisms of the coatings during fatigue are also discussed in conjunction with the hardness,elastic modulus, and fracture toughness, as well as deposition processes. The dynamic nanoindentation fatigue test used in this study can be satisfactorily used to simulate and study damage at the head–disk interface.
91(2002); http://dx.doi.org/10.1063/1.1452700View Description Hide Description
The multilayer granular structure has been developed and has proved to be a promising candidate for extremely high-density magnetic recording. Recently, the properties of friction and wear of the structure have been studied and the in-situ nanoscale protection concept has been proposed. In this paper, two series of CoCrPt–C multilayer samples with various interlayer carbon concentration and with/without carbon overcoat (top layer) are compared, having been prepared by using facing target sputtering (FTS) and normal dc sputtering (DCS), respectively. The corrosion resistance of the sample is investigated using environmental and electrochemical methods. Optical microscopy and time-of-flight secondary ion mass spectrometry are used to characterize the corrosion test samples. For the samples prepared by FTS, both top and interlayer carbon can provide protection for the media. In terms of the samples prepared by DCS, the carbon layer may increase the porous density during the corrosion process. It is concluded that the ratio of the carbon is the most important consideration in nanoscale protection for the granular thin film media. Raman spectroscopy results further confirm the conclusion.